Various embodiments of plug and socket electrical connector systems having plug connectors and complimentary socket mating connectors are conventionally known. Plug connector systems serve to produce releasable electrical or optical connections between the plug connectors and the socket mating connectors. Variations of the conventional plug connector systems have a locking mechanism that secures the plug connector to the socket mating connector in order to prevent unintentional or unauthorised separation of the plug connector from the socket mating connector. However, such conventional locking systems only provide limited utility, because they can often be unlocked unintentionally by normal operating actions. Unintentional separation of the plug connector and socket mating connector is thereby possible in spite of the locking mechanism.